What do you mean "unable to view"? Is the mail there, and when you click on it bad things happen? Is it not there at all? What about plain text emails? Is it all HTML emails are just some? Are they meeting requests or just regular messages?

Sorry I should have been a little more clear. When I get a message that has HTML code and view that message in outlook through the connector, the message is displayed as plain text and all formatting is hidden. The same email viewed in the Zimbra web interface shows the formatting correctly. This is not a problem with an outlook setting since other accounts (IMAP) can show HTML emails correctly. I will try to get the logs today but I have never looked at these specific logs before so if you have any clues on what type of messages I am looking for that would help.

Can you enclose some screenshots of a "good" message in the web client, and a "bad" message in Outlook? Also, the first thing to do is to get a "Show Original" of the message. You can get this from the web client, but also, as of 5.0.5, you can do it in Outlook. In Outlook, right click on the light blue empty area at the top to get Addin command bars, and check Zimbra Support. Then select the message and hit the "Show Original" button on the left hand side. You will be asked to authenticate. Then copy the text that comes up in your browser, and send it. If this doesn't help, then we can get ZCO logs. Unless there is sensitive material in there, you don't have to worry too much about what's in the ZCO logs -- just send them to us.

I believe that Outlook is blocking these pictures. Perhaps you have an anti virus program or something that is causing this? This is the same thing that happens when you right click on an email, choose Junk E-mail, and click Add Sender to Blocked Senders List.

I just solved this for a customer... the problem is AVG Antivirus v8.0. It has a "Certification" feature where it will append some text to each incoming email message that says something to the effect, "This email has been scanned and is clean." The rewriting of the email with that signature somehow causes Outlook not to recognize it as HTML any more.

The solution is to go into AVG's advanced settings, and under the options for email scanning uncheck the box for certification of incoming email.

I should add that this setting will only affect future incoming email. Anything already received and rewritten will still not render in HTML.